Unable to understand "Popen" in python -

i python newbie , looking around understanding popen. have following python code snippet tries directory name , open them. but, not understanding parameters given in popen.

directory = sys.argv[1] if directory == "":   print "proper usage python mycode.py <directory_name>"  p = subprocess.popen(["find", "./" + directory, "-name", "log*"], stdout=subprocess.pipe) output, err = p.communicate() foutput = output.split("\n")